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First time builder: Candu Junior Mini Tugboat

Hi all! I've looked at wooden boats before and briefly considered building one, but I got bit hard a few weeks ago while at the new waterfront restaurant at Disney Springs:

Most importantly, my wife agreed that it would be a cool project!

It's a design that long timers here probably recognize as a Berkeley Engineering Perfect 10. I ordered the study plans from them, and decided that the Candu Junior was the right size and complexity for my time, space, and abilities. I was especially impressed by the look of this one (which is actually a Candu-EZ):

My first step was to order the full plans and build the whole thing piece by piece in CAD so that I understood the plans well. I finished that about a week ago:

There's still some details to be done but at this point I'm pretty happy with the lines. I've changed some of the lines to better suit my tastes and work better with the CNC machine that I have access to. I've started programming some panels, but I decided that the best first step would be a nice straight and firm foundation fixture:

This will encapsulate the box keel and assist in getting the right curve to the hull floor, a good seal between the floor and the keel, and a nice straight stem.

Hopefully I'm off to a good start. Any advice or encouragement you can offer is welcome. I'm thinking of using West System Epoxy instead of the Polyester Resin that the plans note, as I see that epoxy has been used successfully by several builders, and is more standard now than in 1997 when the plans were drawn.

Re: First time builder: Candu Junior Mini Tugboat

Good on you and welcome to the forum.

We lurrrve pictures, here is how to post them:

POSTING PICTURES
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It really is quite difficult to build an ugly wooden boat.
The power of the web: Anyone can post anything on the web
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Re: First time builder: Candu Junior Mini Tugboat

Looking forward to see your build, that little red and black tug isn't a Can-du, the guy that built it looked at a Berkely and decided he wanted something more seaworthy, I have the article somewhere, it's really well done with a 30hp diesel and a proper displacement hull.https://www.youtube.com/watch?v=rkEKWgX3Xok

Re: First time builder: Candu Junior Mini Tugboat

Re: First time builder: Candu Junior Mini Tugboat

First beginner question: What does Epoxy *not* stick to? I'll hopefully glue the scarf joints for the hull bottom this weekend. Should I put wax paper on the floor underneath? Plastic painter's cloth? I'm assuming that a few well placed 5 gallon buckets of water on top will be enough to hold everything in place?

While I'm asking potentially dumb questions, is it OK to temporarily fit check pieces with regular nails and then use a nail set to drive them deep in before taping the joints for real? I understand that may offend the no-fastener purists, but as the nail eventually rusts will it bleed out into the finished surface or is it locked away for most of eternity under the epoxy?

Re: First time builder: Candu Junior Mini Tugboat

Thanks for the advice. I think that last picture alone is enough to scare me straight :-)

I have to admit I'm pretty nervous about messing with epoxy ... not sure why. I guess I don't like working under time pressure. Well, what's the worst that can happen? (Assuming I'm safe about it :-) )

Re: First time builder: Candu Junior Mini Tugboat

West Marine is the only local supplier of Epoxy that I've found so I headed over there after work and picked up a gallon of West System with the slow hardener and did a test with some of the scrap from my cuts.

I glassed about a 5" section, bonded about a 3" square section and set the hardener on top of it, and just gooped some out on the other side to see what it did, what the surface tension was, and how fast it naturally spread.

Then I left about 0.5" in the cup just to see how hot it would get.

It took about an hour to set up to where I couldn't move the joint anymore. (72-ish degrees out and a tiny bit humid).

Re: First time builder: Candu Junior Mini Tugboat

Originally Posted by DeniseO30

Using CNC to reproduce the plan is cool in many ways but I wonder if it crosses the "permission to copy/reproduce" someone's design?

No more so than transcribing / lofting points onto a piece of plywood would be. Sharing the CAD or CNC files would be another story, but they're kind of machine specific so hardly useful to others. Even that is probably more immoral than illegal. You can only really get into trouble if you start selling reproductions.

Originally Posted by DeniseO30

Step scarfs? Compared to 7-1 angle scarf joints?

Yes, my CNC can only do plunge routing or 45 degree angles. The point is to increase the area that gets glued, and a 6" wide step joint in a 0.5" panel is for most practical purposes the same as a 12-1 angled scarf. There might be some notch sensitivity compared to a continuous angled joint, but that kind of thing really only comes into play if you're trying to design the lightest boat possible with low safety factors.

Re: First time builder: Candu Junior Mini Tugboat

I inspected the test joint I made last night and couldn't break it. interestingly, a small dime-sized runoff of epoxy had run over the edge onto the piece of plywood I had underneath protecting my work surface. When I separated that, a chunk of the underlying wood pulled out. I guess the glue really is stronger than the material underneath!

Feeling confident, I went ahead and joined the three hull pieces. I'm going away for a long weekend so this will have plenty of time to cure ...

Re: First time builder: Candu Junior Mini Tugboat

The scarf gluing turned out very well, and I glued the motor board together last night.

Also, I've been keeping a detailed construction log of time (including all design, research, reading, experimentation, and building) and costs, the totals of which I thought might interest people. So far I have spent 84 hours and $1188.68. This was about 50 hours of reading books and the plans, 20 hours in CAD and CNC programming, and 15 hours of building. I'll keep this totaled up as I post more information.

Re: First time builder: Candu Junior Mini Tugboat

I got the hull bottom fiberglassed tonight. There's a couple of sections with some fairly large air bubbles. (1" x 3" or so). I'm assuming I can just cut these out tomorrow with a carpet knife and then patch them over?

Re: First time builder: Candu Junior Mini Tugboat

The cnc thing looks cool, but I don't like the stepped "scarf" which is of course not a scarf at all. Your stepped joint will create 2 hard spots, I'd have thought. It will go together fine, but as the timber is repeatedly stressed in use I fear that hairline cracks will appear, allow water in, which will rot the wood, and we will all be sad.

Re: First time builder: Candu Junior Mini Tugboat

Originally Posted by mirrordude

I got the hull bottom fiberglassed tonight. There's a couple of sections with some fairly large air bubbles. (1" x 3" or so). I'm assuming I can just cut these out tomorrow with a carpet knife and then patch them over?

are you using a squeegee? Less is more in this case too much epoxy will float the cloth and cause the bubbles.

Re: First time builder: Candu Junior Mini Tugboat

Originally Posted by DeniseO30

are you using a squeegee? Less is more in this case too much epoxy will float the cloth and cause the bubbles.

I'm using the west system metal roller. I think that I'm glopping the epoxy on too thick in one pile, assuming that I can evenly spread it out from there using the roller. I'll be a bit more judicious in the future.

Also, including the fiberglass that just arrived, some more epoxy, and some clamps, I'm up to 88 hours and $1412.82

Re: First time builder: Candu Junior Mini Tugboat

Time for an update! This weekend I got the keel built. I nailed everything together (leaving the nail heads 1/8" out for later removal), and then loosened all the joints about 1/32" by tapping them from the inside so the epoxy would have somewhere to go, then taped up the bottom edges to keep the resin inside. This worked fairly well, although I got some leaks. I then mixed up some filler to experiment with making fillets. Apparently I need some work on my cosmetic technique, so it's a good thing that no one will ever see this once I put the hull on. After about 4 hours, I flipped it over, removed the nails, and chiseled off the worst runs with a hammer and a screwdriver. Hopefully tonight I'll get to sanding the joints and then using the trim router to put a nice radius on the edges.

I also used a small chunk of 2x4 wrapped in wax paper so that the front would set up in the right shape to take the stem.

Re: First time builder: Candu Junior Mini Tugboat

Originally Posted by DeniseO30

MD, do the plans call for fillet joints?

The plans are pretty vague, it's not even clear whether the inside of the keel was supposed to be glassed (which I did). I added the fillets both because I wanted the practice on a non-cosmetic area, and because the keel will take the biggest beating during planing and when beaching, so the huge amount of strength that the fillet adds to the joints seemed worth the cost and weight.

Re: First time builder: Candu Junior Mini Tugboat

Originally Posted by DeniseO30

Along with Phil's advice, did you know white vinegar removes uncured epoxy from your skin? Acetone on skin is just nasty.

Yes, I've been using vinegar to wash my hands before I put on gloves, and after I take them off, which I do every three batches or so. I'm just using solo cups to mix. I'm also using vinegar to clean the tools when I'm done.

2 hours of sanding tonight and putting a nice 1/2 inch radius on everything. Next step is to dry fit and then glue the hull bottom on.